For Microsoft Xbox 360 owners, Tuesday is Opening Day — the time to skip school, call in sick or take a vacation day for the big game.

Halo 3.

The much-anticipated third and final edition in the Halo video game trilogy — about a super-human soldier, Master Chief, fighting against alien races and parasites — will be released at 12:01 a.m. Tuesday.

An estimated 4 million copies will be sold in the U.S. in a month, says Gamesindustry.biz.

"I've already talked to my teachers and got my assignments for Tuesday. I don't plan on going to class," says Dane Mitchell, 20, a Cincinnati State and Community College sophomore.

"I'm going to pick up the game at midnight from GameStop, go to a friend's house, and play it for 36 hours," he says. "That's what we did before, when Halo 2 came out, my senior year in high school. I can't believe my parents let me skip school to play it."

Like Mitchell, Neil Godwin, 21, of Milford, Ohio, reserved his copy more than a year ago. He's taking a vacation day Tuesday from his job as a Kroger computer help desk analyst to play Halo 3 all day with his brother.

All the Halo hype — with Burger King, Mountain Dew, NASCAR and Pontiac promotional deals — has made this game release the biggest cultural phenomenon since Harry Potter and the Deathly Hallows arrived in July.

Eager customers will line up to get a copy Monday, or attend launch parties at their favorite video game stores Monday night. Best Buy in Florence, Ky., and 23 area Game Stop stores will open at midnight to sell the Microsoft title, the most-wanted video game by 14-to-17-year-olds, according to national retailer Game Crazy.

"At my school, at least 50 kids are getting it at the midnight release," says Sean Faust, 17, a high school senior from Alexandria, Ky.

"I'm not going to lie. I know about 15 kids who are going to skip school Tuesday, maybe even myself," Faust says. He'll nap 3-11 p.m. Monday, buy his copy at midnight and play until dawn — or much later.

"You've been wanting it for so long, that once you get it you just don't want to put it down. I might just keep playing it," Faust says.

University of Cincinnati marketing major Dave Durham predicts that "about 25% of the students won't be in class on Tuesday" because of the Xbox factor.

"I know a couple people who are taking the whole week off on vacation," says Durham, 21.

Durham, however, plans to make his 8 a.m. statistics class Tuesday. He's one of the lucky Pontiac giveaway winners who will have Halo 3 copies delivered to their homes Monday.

Durham and fellow Pontiac contest winner Luke Mars, 20, of Hamilton, Ohio, will spend the night playing Halo 2 with customers at the independent Game Junkie north of Cincinnati, which will be open for 33 hours straight through Tuesday night.

"I played the Halo beta test in May, and loved it. I played it every day," Mars says. "Even though I won the game, I'm still going to get the collector's version at midnight with the little helmet to hold your Halo games."

Mars, a warehouse worker, says his friends love Halo because they can play against each other — or online with and against people around the world. Players communicate with each other through a headset.

"The game never gets old, because you play against different people around the world. Each time you play, it's a different experience," says Brian Robbe, 30, of Cincinnati. "Other games, after you master them you put them away on a shelf. But not Halo."

Robbe will pick up his copy at Best Buy on Monday night, and play for a while. But he plans to be at his desk Tuesday morning in Kentucky at Cengage Learning, providing technical support for teachers and students.

"I thought about taking the day off, but it's a busy time for us," Robbe says. "But you know, on Tuesday, we might not be getting a lot of calls from students."